Rick Santorum won the Alabama and Mississippi primaries Tuesday, helping him lock up his position as the chief conservative alternative to front-runner Mitt Romney in the race for the Republican nomination to challenge President Barack Obama.

The victories were a blow to Romney, who was running third in both states and had hoped to show he could muster the support of evangelical Christian voters in America's Deep South. But they were especially bad news for Gingrich, who desperately needed a win to show he remains a viable candidate.

``We're on our way to victory tonight; we're on our way to victory in this election,'' Santorum exulted before cheering supporters in Lafayette, Louisiana, which holds its primary March 24. He said it was time for conservatives to unite in an effort to defeat Romney.

In Alabama, with 76 percent of the precincts counted, Santorum was pulling 35 percent of the vote, Gingrich had 30 percent and Romney 28 percent. Returns from 92 percent of Mississippi's precincts showed Santorum with 33 percent, Gingrich 31 percent and Romney 30.

The fourth candidate, Texas Rep. Ron Paul, was not competing actively in the two contests and lagged far behind in single digits.

Romney still holds a commanding lead in delegates to the national convention in Tampa, Florida, in August. The former Massachusetts governor is much better funded and has a superior campaign organization. What's more, he carries the backing of the party establishment. But the conservative base distrusts his one-time moderate views on important social issues like abortion and gay rights.

Slower still to fall in behind Romney have been voters in the Deep South, where he has yet to win a primary. He won in Virginia, where Santorum and Gingrich failed to qualify for the ballot, and in Florida, where he carried counties with many transplanted retirees from northern states but lost those regions in northern Florida most culturally aligned with the old South.

A win in either Mississippi or Alabama would have eased concerns that the Harvard-educated Mormon cannot win over the party's most conservative and evangelical Christian voters, who play an outsized role in both Alabama and Mississippi. In both states, 80 percent or more of voters leaving their polling places said they were born again Christians or evangelical.

The numbers spelled good news for Santorum, a former Pennsylvania senator and deeply conservative Catholic who has captured the hearts of his party's base.

``People of Mississippi and Alabama want a conservative,'' Santorum told reporters in Biloxi, Mississippi, before the results were tallied. pressing his argument that Gingrich should consider stepping aside. ``If they want a conservative nominee for sure, they can do that by lining up behind us and making this race clearly a two-person race outside of the South.''

While Gingrich insisted he plans to remain in the race, his campaign's survival essentially rested on winning both of Tuesday's contests. The former speaker of the House of Representatives has pursued an all-Southern strategy, but he has won only South Carolina and Georgia, the state he represented in Congress for 20 years.

He congratulated Santorum on his victories, and poked fun at Romney. ``If you're the front-runner and you keep coming in third, you're not much of a front-runner,'' he said in Birmingham, Alabama.

Romney, meanwhile, worked to persuade lukewarm Republican voters that he is the most electable candidate.

``I'm the one guy in this race who can beat Barack Obama,'' he told 400 people gathered to hear him speak in Missouri, which holds its caucuses on Saturday.

There were 107 Republican National Convention delegates at stake on Tuesday: 47 in Alabama, 37 in Mississippi, 17 in Hawaii, where caucuses were scheduled, and six more in caucuses in American Samoa.

Santorum's two victories were worth at least 21 delegates. Gingrich won at least 17 and Romney at least 16. The split in Mississippi underscored the difficulty that Romney's rivals face in overcoming his big lead. Each of the three leading contenders won 10 delegates there with seven still to be allocated.

The day began with Romney leading the delegate competition in The Associated Press count, with 454 of the 1,144 needed to win the nomination. Santorum had 217, Gingrich 107 and Paul 47. It will take 1,144 delegates to win the nomination at the Republican National Convention in Tampa, Florida, in late August.

The showdown primaries occurred as new polling showed a steep drop in Obama's approval ratings, a decline that coincides with rapidly climbing gasoline prices as a result of renewed turbulence in the Middle East. The political turmoil across the Mideast and North Africa has been exacerbated by fears that Israel is preparing a military attack on Iran's suspected nuclear weapons program.

A Washington Post-ABC News poll found that 46 percent of those surveyed approve the way the president is handling his job, and 50 percent disapprove. A New York Times/CBS poll found 41 percent approval, and 47 percent disapproval.

Leavening those numbers, the Gallup daily tracking poll had Obama's approval rating at 47 percent. It showed U.S. economic confidence at a four-year high.

On Tuesday, the president, who is unopposed for the Democratic nomination, won the endorsement of the AFL-CIO labor federation. (AP)